CO2 capture and storage (CCS) technology is recognized as the most efficient and direct method for reducing the release of CO2 affecting global warming. In the CCS technology, carbon dioxide is captured from a large volume of CO2 release source, such gas streams, i.e. flue gas streams, produced by fossil fuel-fired power plants, and syngas streams produced by the gasification of coal and reforming of natural gases (commonly called “fuel gases”), and is stably stored.
Technical approaches for capturing CO2, including wet scrubbing using an aqueous solution of monoethanolamine (MEA), ammonia or potassium carbonate (K2CO3), adsorption, such as pressure swing adsorption (PSA) or temperature swing adsorption (TSA), membrane separation, cryogenic fractionation, and the like, are currently researched. However, these methods have problems of high capture cost or difficulty in application to electric power plants or large-scale industries.
Dry regenerable CO2 sorbent technology recognized as an innovative technology for efficiently and cost-effectively capturing carbon dioxide, refers to a technology in which an active component present in a solid sorbent, which is called a dry regenerable CO2 sorbent, instead of a liquid solvent used in a conventional wet chemical absorption, is chemically reacted with carbon dioxide to form a stable compound, followed by isolating pure carbon dioxide using water vapor and an additional heat supply. In addition, the solid sorbent used in the dry regenerable CO2 sorbent technology can be continuously reused through repeated reactions and regeneration of carbon dioxide. Further, in the dry regenerable CO2 sorbent technology, since a fluidized bed process is employed, an installation area is reduced. In addition, in the dry regenerable CO2 sorbent technology, excellent heat transmitting characteristics are demonstrated, little waste water is generated and corrosion rarely occurs. Additionally, the dry regenerable sorbent technology has many advantages in terms of low-price raw materials, design flexibility, environmental friendliness, applicability of low-energy absorption processes, high carbon dioxide sorption capacity with high reaction rate, and the like, so that it can be recognized as a promising technology capable of continuously growing and developing over other technologies in many aspects.
Conventional patents relating to dry regenerable absorbent for carbon dioxide capture include U.S. Pat. Nos. 7,045,483, 6,280,503, 7,314,847, 7,314,847, 7,314,877, 4,515,900, 7,067,456, and 5,214,019, Japanese Patent Application Publication No. 2007-090208, and U.S. Patent Application Publication No. 20070072769, and so on.
The above-mentioned patents mainly relate to an absorbent prepared by combining an active component with a support, an inorganic binder and an organic binder or combining an active component with a support, or an active component itself. The techniques disclosed in these patents may also be applied to quite different application fields, and thus are inappropriate to be applied to a process of preparing a large scale of absorbents due to different preparation methods, including preparation by physical mixture, preparation by supporting, and the like. In particular, the disclosed techniques are inappropriate to be applied to a process of capturing and separating carbon dioxide while solid absorbent particles are continuously transported between absorption and recycling reactors. Therefore, the techniques are inefficient to be applied to industrial processes of releasing a large amount of carbon dioxide, such as thermal power generation plants, iron and steel industry, petrochemical plants and cement plants.
U.S. Pat. No. 782,059, Japanese Patent No. 4181132, Chinese Patent No. 200410101564.0 and Korean Patent No. 10-0620546, issued to Korea Electric Power Corporation (KEPCO), disclose methods for an absorbent capable of absorbing CO2 at 50 to 110° C. and recycling CO2 at 80 to 180° C., the absorbent produced by spray drying a raw material including an active component of an alkali metal or alkaline earth metal compound and a variety of supports. CO2 may also be removed by an absorbent containing an amine compound in a solid porous support in addition to a metal compound based solid absorbent. U.S. Pat. Nos. 5,492,683 and 5,876,488 disclose solid carbon dioxide absorbents containing liquid amine compounds reacting at room temperature. U.S. Pat. No. 4,810,266 discloses removal of CO2 in a room temperature range using a solid absorbent containing an amine compound in a carbon body.
In addition, WO2004/054705 discloses a solid absorbent for capturing CO2 using an amine compound physically adsorbed or chemically connected to a surface of mesoporous silica, and U.S. Pat. Nos. 6,908,497 and 6,547,854 disclose methods for preparing a solid absorbent receiving an amine compound into a surface-treated support.
Korean Patent Application No. KR10-2011-0006073 discloses a method for preparing porous silica having a micropore and mesopore structure and a CO2 absorbent receiving an amine compound into the prepared porous silica.
The above-mentioned patents disclosing solid absorbents (or sorbents) containing amine compounds mainly relate to an absorbent prepared by adding an active component to a support or an active component itself, and thus are inappropriate to be applied to a fluidized bed or high speed fluidized bed dry capturing process of capturing and separating CO2 while solid absorbent particles are continuously transported between absorption and recycling reactors. Thus, the disclosed techniques are inappropriate in view of morphology or performance to be applied to efficiently, cost-effectively capture CO2 in a gas streams having a low partial pressure of CO2, such as a flue gas. Accordingly, it is necessary to develop technology for efficiently, cost-effectively capture CO2 in a large amount of flue gases.